1. Field of the Invention
The present invention relates to a clock spring connector used in an automotive steering system and utilizing cables for establishing an electrical connection between a stationary member and a movable member.
2. Description of the Prior Art
In a clock spring connector are generally used flexible cables for electrical connection between a stationary member and a movable member rotatably attached to the stationary member, which is used for example as an electrical connection device in an automotive steering system.
A type of clock spring connector has been known in which a flat cable comprising a plurality of conductors laminated into a pair of band like films is loosely stored in a spirally wound state in a cable stowage section provided between a stationary member and a movable member, one end of the flat cable being fixedly attached to an outer peripheral wall formed on either one of the stationary member and the movable member, and the other end being fixedly attached to an inner peripheral) wall formed on the other member.
This clock spring connector is capable of coiling the flat cable stowed in the cable stowage section, to the inner peripheral wall side and displacing a section of the flatcable into the outer peripheral wall side in accordance with the direction of rotation of the movable member when the movable member is rotated. Therefore, within a range from the fully coiled state of the flat cable on the inner peripheral wall side to the fully displaced state of the flat cable on the outer peripheral wall side, it is possible to constantly maintain an electrical connection between the stationary member and the movable member which make relative rotation, giving almost no tension to the flat cable.
Since the clock spring connector of the aforementioned constitution coils and uncoils the flat cable by utilizing a difference in diameter between the outer peripheral wall and the inner peripheral wall, the length of the flat cable can be decreased by increasing this difference in diameter when the amount of rotation of the movable member is held unchanged. However, the inner peripheral wall diameter is determined simply and solely from the diameter of a rotating shaft on which the clock spring connector is to be mounted, for example the diameter of a steering shaft of an automobile. In the meantime, since the outer peripheral wall can not be provided with so large a diameter because of a demand for the use of a compact steering system, it is impossible to increase the difference in diameter between these outer and inner peripheral walls. Therefore, this type of clock spring connector generally requires a long and large flat cable, which, however, is difficult to manufacture, resulting in a high total cost of the clock spring connector.